callbacks_disabler.rb

module ActiveRecord
  module CallbacksDisabler
    extend ActiveSupport::Concern

    delegate :callbacks_disabled?, :without_callbacks, to: 'self.class'

    # `run_callbacks` is the core of ActiveSupport callbacks system: in order for a method `foo`
    # to have its callbacks triggered when called, the implementation has to look like this:
    #
    #     def foo
    #       run_callbacks(:foo) { do_something }
    #     end
    #
    # Overriding it so that it does a plain `yield` is enough to completely skip callbacks.
    def run_callbacks(*)
      if callbacks_disabled?
        yield if block_given?
      else
        super
      end
    end

    module ClassMethods
      def disable_callbacks
        @@disable_callbacks = true
      end

      def enable_callbacks
        @@disable_callbacks = false
      end

      def callbacks_disabled?
        @@disable_callbacks ||= false
      end

      def without_callbacks
        disable_callbacks
        yield
      ensure
        enable_callbacks
      end
    end
  end
end

ActiveSupport.on_load(:active_record) do
  ActiveRecord::Base.send(:include, ActiveRecord::CallbacksDisabler)
end